The modulation and demodulation of fm signals may employ an oscillator whose frequency varies with the modulating or control voltage. In order for the demodulated signal to faithfully reproduce the original modulation it is necessary to have the frequency vary linearly with the control voltage in both the transmitter and the receiver. Oscillators whose frequency variation is produced in accordance with a control voltage are called voltage controlled oscillators and many of these circuits employ a varactor diode as the voltage responsive variable reactance component. While the varactor diode is a popularly used element in such circuits, it is rather expensive and, in certain applications such as small, hand-held cellular telephones where only a low supply voltage is available, there may not be sufficient voltage available to permit the varactor diode to undergo a sufficient range of reactance variation to produce the desired frequency excursion of the oscillator. In addition, it is desirable to have the frequency excursion vary linearly with the control voltage. Accordingly, an alternative to the use of the varactor diode in voltage controlled oscillators circuits is desirable.